Why is it important to supply soft water to wet type vacuum pumps?

Well, first off, most manufacturers of this type of vacuum system, will specifically state that their warranties are null and void if hard water is used in their products. Example:

*Apollo Dental Products by Midmark

“On vacuum products, the warranty does not cover failures due to hard water deposits. Failure to follow installation and operation procedures will void warranty.”

Our first recommendation is to install a dry type vacuum system in place of a wet type system to avoid the water use. Most of these machines can gulp and discharge a gallon of water per minute per head. (1 gpm per head) When you have to run all of that water through a softener, it ends up consuming quite a bit of salt. So the best alternative is to eliminate the wet vacuum system, eliminate the water usage, and eliminate the need for a water softener.

However, for those of you who have wet type pumps it is essential that you have soft water plumbed to your vacuum pump for the following reason:

Inside of a vacuum pump is an impeller. This impeller is offset to the side of the pump housing. Many of these pumps have paper thin tolerances between the impeller and the side wall of the housing. Hard water deposits build up on the impeller as the vacuum pump runs. Eventually these deposits accumulate to the point where the impeller rubs against the housing. This buildup has a ceramic hardness to it, and causes the pump to “freeze up”.

We have a motor rebuilder that has some good solid techniques that they use to repair these pumps, but it is still a costly repair and sometimes the damage is so severe that the pump just needs to be replaced. Below is a picture of the inside of a vacuum pump. You can see how close the impeller sits to one side of the housing.
VacPumpImpeller

 

Hard water can damage a new vacuum pump within a year or two of use, or it can take several years depending on how hard your water actually is.
So, just make sure your wet type pump is fed by soft water not hard.